Self-attaching fastener and method of securing same to sheet material

ABSTRACT

An assembly is disclosed having a simple, standard fastener secured to sheet material such as sheet metal. A support strap is integrally formed in an offset relationship with the sheet material, and opposite sides of the fastener are deformed to interlockingly engage the remainder of the sheet material. A method and apparatus are also disclosed for securing the fastener to the sheet material in substantially one operation, including alternate manual and automatic means for feeding fasteners to such apparatus.

This application is a continuation of application Ser. No. 607,949,filed May 7, 1984, now abandoned which was a divisional application ofpending prior application Ser. No. 373,621, filed Apr. 30, 1982 nowabandoned.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a self-attaching fastener and more particularlyto a threaded fastener that is forcibly mechanically interlocked orclinchingly attached to a portion of sheet material, and to apparatusand a method of assembly thereof.

Reference is made to my related patent application, Ser. No. 184,951,filed Sept. 8, 1980, the disclosure of which is incorporated byreference herein. Said application Ser. No. 184,951 is now abandoned infavor of its continuation application Ser. No. 495,440, filed May 17,1983, which issued on July 17, 1984, as U.S. Pat. No. 4,459,753. Thepresent invention disclosed herein includes variations on the inventiveprinciples disclosed in said related application.

It is frequently desirable to secure objects to a member formed from arelatively thin sheet of material, such as sheet metal. Because suchsheet material is generally too thin to form a threaded hole therein bydrilling and tapping, a threaded female fastener or nut is frequentlywelded or otherwise secured to such sheet material, thus allowing a malefastener to be threadably secured thereto.

Alternatively, it may be desirable to provide a threaded male fastenerextending from such sheet material in order to allow another object tobe mounted thereto by means of a threaded female fastener. In such acase, the head of a bolt may be welded or otherwise secured to suchsheet material.

In one known method of securing a threaded fastener to sheet material, aspecially formed clinch nut is fabricated with a pilot portion extendingfrom one of its faces. The pilot is smaller than the remainder of thenut and thus forms one or more shoulder portions thereon. The pilot isinserted into a preformed opening in the sheet material and deformed toflow outwardly, thereby interlockingly engaging the edges of thepreformed hole in the sheet material.

In another method of securing a threaded fastener to sheet material, aspecially formed pierce nut with a pilot is provided which is speciallyadapted to pierce or punch an opening as the nut is forcibly urgedagainst the sheet material. Specially formed dies on a press apparatusdeform the sides of the pilot and the opening in the sheet material toform a clinch-type engagement therebetween. Such specially formed andfabricated pierce nuts may also include shouders on the main portion ofthe nut for abuttingly engaging the sheet material in order to attain amore even stress distribution, thereby strengthening the joint betweenthe nut and the sheet material.

The above-described methods and apparatus for securing a fastener tosheet material suffer the disadvantage of requiring an expensivespecially formed nut or fastener. Such methods and apparatus also tendto weaken the sheet material because of the necessity of removing asubstantial amount of sheet material in order to form the opening inwhich the fastener is received. In a high production environment, theyalso create a considerable amount of scrap.

The present invention overcomes the above disadvantages by allowingstandard fasteners such as ordinary nuts or bolts to be secured to asheet material member, thereby eliminating the need for the expensivespecial fasteners described above. In the disclosed embodiment of theinvention, a standard off-the-shelf square nut or a square-headed boltis secured to such sheet material, frequently without preforming anopening in the sheet material, thereby eliminating or minimizing theattendant scrap. In accordance with the present invention, the sheetmaterial is sheared by means of the coactive force of a pair of cuttingmembers and the edges of the fastener along opposite sides of thefastener to form a support strap therebetween. This strap, which remainsintegral with the sheet material, is simultaneously forcibly urged intoan offset position relative to the plane of the remainder of the sheetmaterial and preferably abuttingly conforms to at least one of the facesof the fastener. The opposite sides of the fastener, adjacent thesheared portion of the sheet material, are deformed to interlock thefastener to the sheet material.

Thus the present invention provides a method and apparatus by whichordinary fasteners can be rigidly secured or attached to a sheetmaterial member without the need for specially formed fasteners.Furthermore, because the only sheet material removed (if any) is thatresulting from the punching of a hole in the support strap whichcorresponds to the aperture through a female fastener, or which receivesthe stud portion of the male fastener, the sheet material is notsubstantially weakened by the forming or pressing operation andsignificantly less scrap is generated.

These and other advantages of the invention will become readily apparentfrom the following discussion and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the fastener assembly of the presentinvention, illustrating a female fastener secured to sheet material.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1.

FIG. 4 is a perspective view of an alternate fastener assembly accordingto the present invention wherein a male fastener is secured to sheetmaterial.

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4.

FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 4.

FIG. 7 is an elevational view of the press and forming die portions ofan apparatus for securing a fastener to sheet material according to thepresent invention.

FIG. 8 is a partial perspective view of the forming die portion of theFIG. 7 apparatus, illustrating a retaining spring arrangement forholding a female fastener.

FIG. 9 is a view similar to that of FIG. 8, illustrating an alternateretaining spring arrangement for holding a male fastener.

FIG. 10 illustrates an alternate fastener feeding mechanism for theapparatus of FIG. 7.

FIG. 11 is a view taken along line 11--11 of FIG. 10.

FIG. 12 is a cross-sectional view of the fastener and the press and dieportions of the FIG. 7 apparatus, prior to the forming stroke.

FIG. 13 is an enlarged cross-sectional view similar to that of FIG. 12,but illustrating the fastener and forming components at the end of theforming stroke.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 through 13 of the drawings illustrate various embodiments offasteners secured to sheet material members according to the presentinvention, as well as an apparatus for forming the assembly. Forpurposes of illustration, the drawings illustrate embodiments wherein astandard square nut and a standard square-headed bolt are secured to thesheet material. One skilled in the art will readily recognize, however,that other fasteners having other shapes may also be secured to sheetmaterial in a similar manner.

FIGS. 1 through 3 illustrate a fastener assembly 10 in which a femalefastener 12 is rigidly secured to sheet material 14. Prior to assembly,fastener 12 is a simple inexpensive square nut having a central threadedhole 32, as is shown in phantom lines at 12a. Sheet material 14 includesan integral support strap 16 positioned in an offset relation relativeto the plane of the remainder of the sheet. Support strap 16 is offsetby means of shearing along the opposite sides 18 of fastener 12, asindicated at reference numeral 20. The sides 18 of fastener 12 aredeformed so that the fastener material flows outwardly to form a pair ofspaced protrusions 22 which interlockingly engage the sheared edges 20and so that a pair of flared lips 21 are formed along sheared edges 20.

The edges of support strap 16 are also preferably deformed in adirection toward and slightly around the fastener, as shown at 24, tointerlockingly retain fastener 12. An opening 30 is punched or otherwiseformed in the support strap 16 in alignment with hole 32 in the fastenerto allow a bolt, stud or screw to be threadably inserted into hole 32for mounting another member (not shown) to the assembly.

FIGS. 4 through 6 illustrate a fastener assembly 40 in which a malefastener 42 is secured to sheet material 14. In its original form,fastener 42 is a simple and inexpensive square-headed bolt having head44 and threaded stud 46. The original form of head 44 is indicated inphantom lines at 44a. Head 44 is secured to the sheet material in amanner similar to that described above in connection with femalefastener 12 except that stud 46 protrudes through opening 30 in supportstrap 16. Alternatively, however, fastener 42 may be oriented in aposition opposite to that shown in FIGS. 4 through 6, with stud 46extending in the opposite direction, and thus support strap 16 would notrequire an opening 30. Because fastener 42 is otherwise secured to sheetmaterial 14 in the same manner as is described above in connection FIGS.1 through 3, corresponding reference numerals are used in FIGS. 4through 6.

The embodiments of FIGS. 1 through 6 accommodate the use of standardthreaded fasteners with no special configurations or pilots beingrequired. The cost of such standard fasteners has been found to beapproximately one-half of that of many specially shaped piercing-typefasteners. Furthermore, the resulting strength of the joint created bythe fastener assemblies of the present invention have been found to besuperior to joints formed using many specially formed fasteners.Specifically, the pull-out strength of the joint, which is the strengthof the joint in resisting a force tending to pull the fastener upwardlyaway from the sheet material, as shown, has been found to besignificantly greater than that of many prior art fastener assemblies.Such improvement is believed to be due to the full interlockingengagement with the sheet material on two opposite sides of the fastenerand to the support strap 16 extending over one face of the fastener.Similarly, the push-out strength, which is the strength of the jointresisting a force tending to push the fastener away from the sheetmaterial in the opposite direction, has also been found to comparefavorably with that of the prior art fastener assemblies.

In FIGS. 7 through 13, an exemplary joint-forming apparatus 60 is shownfor purposes of illustration. One skilled in the art will readilyrecognize, however, that other similar apparatus may be used toaccomplish the objectives of the present invention.

Apparatus 60 includes a punch assembly 62, shown in FIG. 12 in apartially lowered position, and an anvil assembly 64. Punch assembly 62is operatively connected to a ram or press apparatus 66 which drives itin a reciprocating manner, and also includes a keeper member 68 whichhas a bore 69 extending partially therethrough for slidably receiving acircular punch 70 and a tubular driver member 72 therein. Driver member72 includes a die portion 74 on its lower end (as shown) and is retainedwithin bore 69 by a retaining member 76 which allows limitedreciprocating movement and prevents rotation of the driver member 72within bore 69. Punch 70, at its upper end (as shown), abuttinglyengages the closed end of bore 69. A compression spring 78 biases drivermember 72 out of bore 69, thereby allowing the driver member to performa stripping function, as will be explained below.

Adjustment nut 116 may be threadably advanced or retracted to adjust thepoint of engagement by punch assembly 62 and thus the stroke length ofdriver member 72. Jam nut 117 lockingly abuts adjustment nut 116 tomaintain its axial position on driver member 72.

As illustrated in FIGS. 3 and 8, a pair of opposed retaining springs 115on driver member 72 resiliently engage opposed sides of female fastener12 to support it in proper alignment with anvil assembly 64, asexplained below. Alternately, as shown in FIGS. 5, 6 and 9, a secondpair of opposed retaining springs 118 are also used to resilientlyengage corresponding sides of male fastener 42. Springs 118 are shorterthan springs 115, to avoid interfering with the forming of protrusions22 on the fastener, and thus engage the sides of fastener 42 only whenhead 44 is in its original form 44a, as shown in FIG. 5. One skilled inthe art will readily recognize that similar retaining springarrangements may be employed for fasteners having other than four-sidedheads.

Anvil assembly 64 includes a fixed die member 84 having a die surface 86thereon. Die portion 74 and die member 84 each have a pair of spacedshoulders 75 and 85, respectively, which deform the sides of thefastener, as shown in FIG. 13, to form the protrusions 22 thereon (seeFIGS. 2 and 5). A pair of cutting members 88, in the form of die blades,are pivotally connected to the fixed die member 84 by means of a pair ofpivot pins 90. Die member 84 includes a pair of integral shoulders 114slidably abutted by corresponding surfaces 112 on cutting members 88.Thus, any vertical forces on the cutting members 88 are thus transmitteddirectly to die member 84 and are not absorbed by pins 90, as is fullydescribed in my above-referenced related applications. A correspondingpair of compression springs 92 bias the cutting members 88 toward theirpositions adjacent die surface 86, as shown in FIGS. 12 and 13. Fixeddie member 84 also includes a bore 96 extending therethrough, whichcommunicates with bore 117a in an adjusting screw 119 and is configuredto accommodate punch 70 and to provide for disposal of the blank 102 ofsheet material which is removed by punch 70.

For purposes of illustration, the operation of apparatus 60 is describedherein in connection with the attachment of a female fastener to thesheet material, substantially in one operation. As will be readilyrecognized by one skilled in the art, however, the operation ofapparatus 60 in connection with the use of a male fastener is similar,with the minor exceptions noted below.

FIGS. 10 and 11 illustrate an automatic fastener feed apparatus 140 foruse with forming apparatus 60 in lieu of the retaining springs discussedabove. A fastener feed chute 142 serially transports a number of femalefasteners 12 by gravity or under air pressure to a fastener carriermechanism 144. A retractible pin 148, which may be actuated in anysuitable manner, holds back the supply of fasteners until the carriermechanism is cleared.

The carrier mechanism 144 includes an opening 150 having across-sectional shape corresponding to the cross-section of the fastenerto ensure proper fastener orientation and alignment with die portion 74and die member 84 during the forming operation. A plurality of balls152, biased by springs 156, extend partially into opening 150 to supportthe fastener until it is engaged by driver member 72. As the fastener isurged downwardly, springs 156 compress and balls 152 retract, and thefastener is forced through opening 150 to engage sheet material 14, asdiscussed below.

One skilled in the art will readily recognize that similar apparatus maybe employed for automatically feeding male fasteners 42 to formingapparatus 60. In such an apparatus, for example, chute 142 would includea longitudinal slot for receiving stud 46, thus allowing head 44 to betransported in a manner similar to that shown in the drawings forfastener 12. Carrier mechanism 144 would also include a correspondingvertical slot to provide clearance for stud 46 at the junction withchute 142.

Referring primarily to FIGS. 12 and 13, the operation of apparatus 60 isas follows. Sheet material 14 is positioned over anvil assembly 64 sothat the area in which the fastener assembly is to be formed liesdirectly below punch assembly 62. Fastener 12 is loaded onto drivermember 72, with punch 70 extending through hole 32 if opening 30 isdesired. The loading of fastener 12 on apparatus 60 may be accomplishedmanually, as shown in FIG. 12, or by means of an automatic feedmechanism, such as that illustrated in FIGS. 10 and 11.

Ram 66 is then further actuated to drive punch assembly 62 downwardly,whereby punch 70 forms opening 30 and die portion 74 forcibly pressesfastener 12 against sheet material 14 (after keeper member 68 has movedinto an abutting relationship with driver member 72). If an openinghaving a larger diameter than the inside diameter of threaded hole 32 isdesired, it may be pre-formed in the sheet material. Blank 102,resulting from the forming of opening 30, drops into bore 96 fordisposal. Thereafter, die portion 74 presses fastener 12 against thesheet material 14 with sufficient force that the leading edges orcorners of the opposite sides 18 coact with the inner edges of dieblades 88 to cause the sheet material to be sheared or lanced alongsides 18. The fastener continues to be forced through the sheet materialto offset support strap 16 in abutting and conforming engagement withthe face of the fastener.

Once support strap 16 contacts shoulders 85 on die member 84, bothfastener 12 and support strap 16 are further deformed between shoulders75 and 85 to cause the material of fastener 12 to begin to flowoutwardly, forming protrusions 22 which interlockingly engage edges 20of the sheet material. As protrusions 22 are formed, cutting members 88are pivoted outwardly as shown in FIG. 13. Continued deformation ofsupport strap 16 and fastener 12 also causes edges 20 to bend toward diemember 84 to form the flared lips 21 shown in FIGS. 2 and 5. A portionof support strap 16 is also deformed to interlock with the sides 18 as aresult of the above deformation.

Driver member 72 restrains the fastener as the punch 70 retracts,thereby aiding in the stripping of punch 70 from hole 32. As punchassembly 62 continues to retract, driver member 72 is raised so that thesheet material may be removed.

The apparatus for attaching fastener 42 to the sheet material is similarto that described above. Because stud 46 protrudes from head 44,however, opening 30 in support strap 16 is preferably pre-punched sothat stud 46 may be inserted therein, and fastener assembly 40 is thenformed as described above. If, however, fastener 42 is to be orientedwith stud 46 protruding away from support strap 16, pre-punching wouldnot be required.

The sheet material may be embossed in an area surrounding the fastener,if desired, to create a flush, generally coplanar relationship betweenthe sheet material and a face of the fastener. Such embossing may beperformed prior to securing the fastener to the sheet material orsimultaneously therewith by means of specially formed die surfaces.

The foregoing discussion and the accompanying drawings disclose,illustrate and describe merely exemplary methods and embodiments of thepresent invention. One skilled in the art will readily recognize fromsuch discussion and drawings that various changes, modifications andvariations may be made therein without departing from the spirit andscope of the invention as defined in the following claims.

I claim:
 1. A method of securing a fastener to sheet material utilizingfirst and second relatively movable die means, said fastener having atleast one face and two opposite sides, each of said sides having an edgethereon, said method comprising the steps of:(a) positioning saidfastener and said sheet material between said first and second diemeans; (b) forcibly pressing said fastener into said sheet material sothat said first die means and said edges of said fastener coact to sheara portion of said sheet material along said sides of said fastener; (c)deforming said sheet material between said sheared portions to form anintegral support strap therebetween in an offset position relative tothe remainder of said sheet material; and (d) deforming a portion ofsaid fastener adjacent at least one of said sheared portions to formprotrusions on at least one of said sides in engagement with saidadjacent sheared portion.
 2. The method of claim 1, wherein the formingof said protrusions also includes displacing said adjacent shearedportion to form a flared lip engaged by said protrusions.
 3. The methodof claim 2, further comprising the step of deforming a portion of saidsupport strap to engage at least one of said sides of said fastener. 4.The method of claim 3, wherein said fastener includes a threadedaperture extending therethrough, said method further comprising the stepof forming an opening in said support strap, said opening correspondingto, and communicating with, said threaded aperture.
 5. The method ofclaim 4, further comprising the step of embossing a portion of saidsheet material around said fastener.
 6. The method of claim 4, whereinsaid forcibly pressing step is preceded by the step of embossing aportion of said sheet material around the area onto which said fasteneris to be secured.
 7. The method of claim 3, wherein said fastenerincludes a stud portion protruding therefrom, said method furthercomprising the steps of forming an opening in said sheet material andinserting said stud portion therethrough.
 8. The method of claim 7,further comprising the step of embossing a portion of said sheetmaterial around said fastener.
 9. The method of claim 7, wherein saidforcibly pressing step is preceded by the step of embossing a portion ofsaid sheet material around the area onto which said fastener is to besecured.
 10. A method of securing a fastener to sheet material utilizinga number of relatively movable die means, said fastener having at leasttwo opposite sides, each of said sides having an edge thereon, saidmethod comprising the steps of:(a) positioning said fastener and saidsheet material between said relatively movable die means; (b) forciblymoving said relatively movable die means toward one another; (c)forcibly urging said fastener into said sheet material as said die meansare moved relatively toward one another so that said die means and saidedges of said fastener coact to shear a portion of said sheet materialalong said sides of said fastener; and (d) forcibly deforming said sheetmaterial between said sheared portions as said die means are movedrelatively toward one another in order to form an integral support straptherebetween in an offset position relative to the remainder of saidsheet material.
 11. The method of claim 10, further comprising the stepof deforming a portion of said support strap to engage at least one ofsaid sides of said fastener.
 12. The method of claim 10, furthercomprising the step of deforming a portion of said support strap into anoverlying engagement with at least a portion of said fastener as saidfastener is forcibly urged into said sheet material.
 13. The method ofclaim 10, further comprising the step of forcibly urging said shearedportions of said sheet material and said sides of said fastener into asecuring engagement with one another as said die means are movedrelatively toward one another.
 14. The method of claim 10, furthercomprising the steps of forcibly urging said sheared portions of saidsheet material and said sides of said fastener into a mechanicallyinterlocking engagement with one another as said die means are movedrelatively toward one another.
 15. The method of claim 10, wherein saidfastener includes a threaded aperture extending therethrough, saidmethod further comprising the step of forming an opening in said supportstrap, said opening corresponding to, and communicating with, saidthreaded aperture.
 16. The method of claim 10, further comprising thestep of embossing a portion of said sheet material around said fastener.17. The method of claim 10, wherein said forcibly urging step ispreceded by the step of embossing a portion of said sheet materialaround the area onto which said fastener is to be secured.
 18. Themethod of claim 10, wherein said fastener includes a stud portionprotruding therefrom, said method further comprising the steps offorming an opening in said sheet material and inserting said studportion therethrough.
 19. The method of claim 18, further comprising thestep of embossing a portion of said sheet material around said fastener.20. The method of claim 19, wherein said forcibly urging step ispreceded by the step of embossing a portion of said sheet materialaround the area onto which said fastener is to be secured.
 21. A methodof securing a fastener to sheet material utilizing a number ofrelatively movable die means, said fastener having at least two oppositesides, each of said sides having an edge thereon, said method comprisingthe steps of:(a) positioning said fastener and said sheet materialbetween said relatively movable die means; (b) forcibly moving saidrelatively movable die means toward one another; (c) forcibly urgingsaid fastener into said sheet material as said die means are movedrelatively toward one another so that said die means and said edges ofsaid fastener coact to forcibly deform a first portion of said sheetmaterial in order to form an integral support strap in an offsetposition relative to the remainder of said sheet material; and (d)forcibly urging a second portion of said sheet material and said sidesof said fastener into a securing engagement with one another as said diemeans are moved relatively toward one another.
 22. The method of claim21, wherein said second portion of said sheet material and said sides ofsaid fastener are forcibly urged into a mechanically interlockingengagement with one another as said die means are moved relativelytoward one another.
 23. The method of claim 21, further comprising thestep of deforming a portion of said support strap into an overlyingengagement with at least a portion of said fastener as said fastener isforcibly urged into said sheet material.
 24. The method of claim 21,wherein said fastener includes a threaded aperture extendingtherethrough, said method further comprising the step of forming anopening in said support strap, said opening corresponding to, andcommunicating with, said threaded aperture.
 25. The method of claim 21,further comprising the step of embossing a portion of said sheetmaterial around said fastener.
 26. The method of claim 21, wherein saidfastener includes a stud portion protruding therefrom, said methodfurther comprising the steps of forming an opening in said sheetmaterial and inserting said stud portion therethrough.
 27. The method ofclaim 26, further comprising the step of embossing a portion of saidsheet material around said fastener.
 28. A method of securing a fastenerto sheet material utilizing a number of relatively movable die means,said fastener having at least two opposite sides, each of said sideshaving an edge thereon, said method comprising the steps of:(a)positioning said fastener and said sheet material between saidrelatively movable die means; (b) forcibly moving said relativelymovable die means toward one another; (c) providing cutting meansassociated with at least one of said die means; (d) forcibly urging saidfastener into said sheet material as said die means are moved relativelytoward one another so that said cutting means and said edges of saidfastener coact to shear a portion of said sheet material along saidsides of said fastener; and (e) forcibly deforming said sheet materialbetween said sheared portions as said die means are moved relativelytoward one another in order to form an integral support straptherebetween in an offset position relative to the remainder of saidsheet material.
 29. The method of claim 28, further comprising the stepof deforming a portion of said support strap into an overlyingengagement with at least a portion of said fastener as said fastener isforcibly urged into said sheet material.
 30. The method of claim 28,further comprising the step of forcibly urging said sheared portions ofsaid sheet material and said sides of said fastener into a securingengagement with one another as said die means are moved relativelytoward one another.
 31. The method of claim 28, further comprising thestep of forcibly urging said sheared portions of said sheet material andsaid sides of said fastener into a mechanically interlocking engagementwith one another as said die means are moved relatively toward oneanother.
 32. The method of claim 28, wherein said fastener includes athreaded aperture extending therethrough, said method further comprisingthe step of forming an opening in said support strap, said openingcorresponding to, and communicating with, said threaded aperture. 33.The method of claim 28, further comprising the step of embossing aportion of said sheet material around said fastener.
 34. The method ofclaim 28, wherein said fastener includes a stud portion protrudingtherefrom, said method further comprising the steps of forming anopening in said sheet material and inserting said stud portiontherethrough.
 35. The method of claim 29, further comprising the step ofembossing a portion of said sheet material around said fastener.